Understanding Sinus Rhythm with Left Axis Deviation

Introduction

When you receive an electrocardiogram (ECG) report stating "sinus rhythm with left axis deviation," you might wonder what it means. Let's break it down in simple terms.

What is Sinus Rhythm?

Sinus rhythm is the normal rhythm of the heart, originating from the sinoatrial (SA) node, the heart's natural pacemaker. A normal sinus rhythm indicates that the heart is beating in a regular pattern, typically with a rate between 60 and 100 beats per minute.

What is Axis Deviation?

The electrical axis of the heart represents the overall direction of electrical activity through the ventricles. It is measured in degrees on an ECG:

• Normal axis: Between -30° and +90°
• Left axis deviation (LAD): More negative than -30°
• Right axis deviation (RAD): More positive than +90°

A left axis deviation means that the electrical impulses are traveling more towards the left than usual.

Causes of Left Axis Deviation

Left axis deviation can occur due to several reasons, including:

1. Normal Variation

• Some individuals, especially older adults, may naturally have a slight leftward deviation without any heart disease.

2. Left Ventricular Hypertrophy (LVH)

• Thickening of the left ventricle, often due to long-standing high blood pressure or aortic valve disease, can alter the heart’s electrical conduction and lead to LAD.

3. Left Anterior Hemiblock

• A conduction block in the anterior fascicle of the left bundle branch can cause left axis deviation.

4. Coronary Artery Disease

• Reduced blood supply to certain areas of the heart (e.g., past heart attacks) can disrupt electrical conduction and shift the axis.

5. Other Causes

• Conditions such as cardiomyopathies, congenital heart defects, or certain medications affecting heart conduction.

What Should You Do Next?

If left axis deviation is found incidentally on your ECG and you have no symptoms, it may not indicate a serious issue. However, if you experience:

• Shortness of breath
• Chest pain
• Palpitations
• Dizziness or fainting

then further cardiological evaluation may be necessary.

Diagnostic Steps

To determine if LAD is a concern, your doctor may recommend:

• Echocardiogram: To assess heart structure
• Blood tests: To check for underlying conditions
• Holter monitor: To track heart rhythm over time
• Further ECG analysis: To rule out conduction blocks or other abnormalities

Conclusion

Sinus rhythm with left axis deviation is a finding on an ECG that may or may not indicate a cardiac problem depending on its cause and associated symptoms. If detected, a cardiologist can determine whether follow-up tests are required.

Source recommendations

1. American Heart Association Guidelines on ECG Interpretation

1. https://www.heart.org/en/health-topics/heart-attack/diagnosing-a-heart-attack/electrocardiogram-ecg-or-ekg
2. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191095
3. https://www.heart.org/-/media/files/affiliates/mwa/kansas-city/kc-cardiac-and-stroke-symposium/2020-event-documents/cardiac-presentations/2-ecg-hockstad.pdf?la=en
4. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191098
5. https://pubmed.ncbi.nlm.nih.gov/19281931/

2. European Society of Cardiology Guidelines on ECG Diagnosis

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines
2. https://academic.oup.com/eurheartj/article/35/39/2733/853385
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Acute-Coronary-Syndromes-ACS-Guidelines
4. https://academic.oup.com/eurheartj/article/39/21/1883/4939241
5. https://www.escardio.org/Guidelines